Initialisations on Booting

The Debian GNU/Linux kernel loads init very early on in the
boot process, using /etc/inittab as its configuration file.
This file defines the default run level and what should be done for
each run level.

If you have a look at the processes running on your system (with the
command line ps or with the graphical Gnome utility
gtop) you will see that the init process has process
identifier of 1 (unless you are running a more secure GNU/Linux where
random numbers are assigned to the processes).

The initialisation table (/etc/inittab) is where system
initialisations occur. This table consists of records with four fields
separated by a colon:

id:runlevels:action:process

The first field is an identifier. The second lists the runlevels for
which this record is relevant. The third is the action to be
performed. The fourth is the command to be run.

In this chapter we look at how the GNU/Linux system is initialised.
See Chapter 11 for an explanation of the boot process and
how to control booting.